Point plotting graphic recorder



A. D. BROWN NOvQ 7, 1967 POINT PLOTTING GRA PHIC RECORDER Filed Dec. 15, 1965 United States Patent 3,351,949 POINT PLOTTING GRAPHIC RECORDER Albert D. Brown, Houston, Tex., assignor, by mesue assignments, to Bausch & Lomb Incorporated, Rochester, N.Y., a corporation of New York Filed Dec. 15, 1965, Ser. No. 513,972 3 Claims. (Cl. 346-94) ABSTRACT OF THE DISCLOSURE A high speed point plotting graphic recorder capable of printing several hundreds of points per minute having a character head resiliently mounted for movement from an at-rest position above a chart to deliver a blow to the chart and then to return to an at-rest position. A body of elastomer is provided below the chart to receive the blows of the character head to cushion such blows and to supply a rebounding force to move the character head back to an at-rest position before it is time to deliver the next blow to the chart.

This invention relates to a high speed point plotting graphic recorder in which the point printing apparatus is arranged so that it can readily plot several hundreds of points per minute with satisfactory resolution of the characters being printed and without mutilating the recording medium.

Point plotting recorders have various uses in the graphic recording art where it is desirable to transfer information to a chart in symbol or digital form rather than in a continuous trace. In such recorders, the printer is moved on a carriage over the chart paper along one or both of the X and Y axes until the null point is sensed, and then the printer is actuated to print the symbol. Unlike the pen in a continuous trace recorder, the printer must then be lifted from the paper and moved to the next point to be plotted or be lifted from the paper to allow for its movement if one of the axes is provided by moving the paper. Since the printer or the paper cannot be moved to the next plot point until the printer is lifted from the paper, the speed at which this lifting occurs becomes a consideration when attempting to provide for high speed graphical recording. I

Heretofore the speed at which graphic recorders can operate successfully has been limited by lack of a means for providing rapid lifting of the printer head after a symbol has been plotted. For example, the printer head is forced down to strike the paper against a spring tension Which causes the printer head to lift to its at-rest position when the downward force, usually from the plunger of a solenoid, is removed. This means has proven unsatisfactory in recorder systems requiring speeds greater than 7 to 10 plots per second.

Furthermore, prior known printing assemblies using such a spring having suflicient strength to by itself return the printer head to its at-rest position at speeds in excess of 7 to 10 plots per second have mechanical stiifness and harshness. Also, such printing assemblies have the problem of misalignment of the character symbol as it strikes the paper so that the symbol does not lay flat on the paper, or moves laterally, as it strikes the paper. Thus, a distinct symbol is not printed. These printers also tend to be noisy and chatter excessively at higher speeds. Also, the hardness of the character symbol becomes an important factor when misalignment occurs at high speeds as a hard symbol will cut the paper and ribbon. A soft symbol, while it would tend to compensate for symbol misalignment, will usually form a mushy character and is not a satisfactory solution.

In the point plotting recorder of this invention, the printer can provide printing speeds in excess of 70 plots per second Without any of the disadvantages of symbol misalignment, mechanical harshness, chatter, mushy characters, or paper cutting referred to above as inherent in other printers at speeds in excess of 10 plots per second It is thus an object of this invention to provide a high speed point plotting graphic recorder which will provide for a rapid lift-off of the printer from the recording medium after a point is plotted.

It is another object to provide such a recorder which Will obtain high plotting speeds and yet print distinct characters without mutilation of the printing medium.

Another object is to provide such a recorder in which the problem of character alignment has been substantially reduced.

Other objects, advantages and features of this invention will become apparent to one skilled in the art upon study of the disclosure, claims and the accompanying drawings forming a part of this application, in which for the purpose of illustration is shown a preferred embodiment of this invention, and in which like numerals are employed to designate like parts throughout the same;

FIG. 1 is a pictorial view showing a portion of a point plotting recorder and especially illustrating the character printer system; and

FIG. 2 is a side view of the character printer assembly shown in FIG. 1 in which the printer is shown in its static position and in which the printer is shown in part in dashed outline to illustrate it striking an ink ribbon to print on the paper.

In the drawings, a carriage or body 1, forming a part of a printer assembly, is slidably supported adjacent the record medium or chart paper 2 by a pair of rods 3 and 4 and is moved along the rods by cable 5. Movement of the cable to position the printer assembly can be caused and controlled by suitable arrangements which can be conventional in character.

A bracket or angle plate 6 is secured to the body to support a leaf spring 7 and a solenoid 8. The leaf spring 7 .is fixedly secured to the angle plate by suitable bolts 9 and has an extending portion on which is mounted a character head 10 having one or more characters 11 thereon. Various ones of these different characters can be selected by rotating the head 10.

Means are provided for applying force to the spring at a point between its connection to the angle plate and the printer head 10 to cause the spring to flex downwardly to cause the character printer to deliver a blow to the medium 2 and imprint thereon. This means is illustrated as the solenoid 8 having a plunger 17 which is biased upwardly by a spring (not shown). Upward movement of the plunger is limited by a suitable stop 11 which is held in place by a bracket 12. The electrical signal for actuating the solenoid can be transmitted to the solenoid by a flexible conductor 13a.

In high speed printing, such as where several hundreds of plots are made per minute, the body 1 is subject to high acceleration and deceleration forces. These will tend to cause the spring 7 to deflect sideways so that the character 11 is not in proper position for printing when the solenoid is actuated. To prevent this, a guide 13 is attached to body 1 and extends through a suitable opening in the leaf spring.

An inked ribbon 14 is provided between the printer head 10 and paper 2. The ribbon is not directly centered beneath the printer head 10 and its character 11 so that the ribbon can be turned over and a difierent section used. The downward movement of plunger 17 and therefore printer head 10 causes the character 11 to strike the inked ribbon 14 and paper 2 and leave a character imprinted thereon.

Although in the preferred embodiment, an ink ribbon is shown between the printer head and the chart paper, the printer itself may be inked or any of the other well-known devices for printing a symbol on the paper may be used.

In accordance with one aspect of this invention, a body of elastomer having substantial rebound properties is placed under the record medium at the point at which a character or plot is to be printed to receive the downward blows of the character printer so as to cushion these blows and to supply a rebounding force to the character printer to cause the printer and leaf spring to move rapidly back to the springs at-rest positioin. Thus, as shown in the drawing, a metal platen or bed 15 is provided beneath the record medium and a strip 16 of the elastomer is situated therein. Only a relatively narrow strip of the elastomer is necessary in the illustrated plotter since the printer assembly moves only in the Y-axis direction. However, in those point plotters where the printers assembly moves in both the X-axis and the Y-axis directions, a sheet of the elastomer coextensive with the printing area will be used.

The elastomer must have sufficient rebound properties, depending upon the speed of recording desired, to cause the printer head and spring to rebound up and out of contact with the record medium in a short enough period of time that the printed head will be out of contact with the medium, and also the ribbon, when one is used, before the printer assembly is moved to position it for the next plot and, also, in a time short enough that the spring and printer head are in their at-rest position before the solenoid receives its next signal to plot. With printing speeds of up to 70 plots per second, it can be seen that this time interval is very short. Various elastomers can be used such as natural rubber, butadiene styrene copolymer, polychloroprene, butadiene-acrylonitrile copolymer, etc. The rebound properties of an elastomer can be determined in a test by dropping a 1.9 centimeter diameter steel ball from a height of 100 centimeters on to a sample 1.9 centimeters thick at 20 C. and measuring the height to which the ball rebounds on the first bounce and expressing this as a percentage of the original height. The optimum rebound percentages for any given recorder can be determined by mere routine test. Generally, low ball rebound percentages are satisfactory for lower printing speeds when using higher power solenoids and higher speeds can be achieved with limited power solenoids by using elastomers with high rebound percentages. Generally, ball rebound percentages of at least should be used and, as a specific example, it has been found that using an elastomer in the range of 40 to 45% ball rebound percentage will permit a character printer to reach speeds of 70 plots per second. The rebound properties for various materials and further reference to he above test can be found in the 195 l1952 edition of the Handbook of Physics and Chemistry.

In a graphic recorder in which the printer assembly is moved at high speeds, the printer assembly should have as little weight as possible to allow for sudden and precise stopping of the carriage and to minimize over-shooting. In this regard, the carriage can be made of a light plastic material. Also, the weight of the solenoid and its location on the carriage are significant in providing stability at high lateral speeds. The solenoid is preferably mounted to help evenly distribute the weight of the printer assembly between rods 3 and 4 and at the same time strike a blow on the leaf spring sufiicient to cause the printer to print. Since it is desirable to keep the Weight of the solenoid at a minimum, the impact force obtainable is generally small. Furthermore, the solenoid stroke should be short, usually or less, so that the plunger can be quickly returned to its retracted position to allow for another plot. Thus, the location of the solenoid is further restricted to a location where the stroke of the solenoid is sufficient in length and power to cause a distinct symbol to be printed. It is also desirable in this regard that the strength of the leaf spring be only enough to hold the printer head in its at-rest position and that the spring be privoted at a point as far as possible from where the printer head is mounted. Both of these factors will aid in keeping the power requirements at a minimum in order to minimize the weight of the solenoid.

Also, in the preferred embodiment hown, resolution is such that up to 40 characters may be printed per inch. Thus, the characters must be sufiiciently small to provide distinct and separate indications for each of their plots. Regardless of the material used for such small characters, the characters themselves are too small to aid in providing rebound from a non-resilient backing surface, but suflicient rebound is obtained when the elastomer described above is used as the backing material. These characters are preferably made of hard rubber but, in any event, they should be of sufficient hardness to print distinct characters. Due to the buffering effect provided by the elastomer backing in conjunction with the paper and the ribbon, the printer prints distinct characters without cutting or mutilation of the paper or the ribbon.

The elastomer also absorbs the noise and chatter normally inherent with high speed printers and serves to minimize the mechanical harshness of the apparatus so as to also length the life span of the other components.

Also, the characters need not be perfectly aligned in a perpendicular relationship with the paper, although they must substantially be so aligned, as the elastomer backing will give a suificient amount from the blow of the printer head to allow the paper and the character to press together and give a complete print.

From the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed 1. In a high speed point plotting graphic recorder having a record medium upon which points are to be plotted, in combination therewith of a printing apparatus for printing said points on said medium at a speed of several hundreds of points per minute comprising a body mounted adjacent said medium, a leaf spring rigidly attached to said body at one locus along its length and having a portion extending from said locus to overlie said medium; a character printer mounted on the extending portion of said spring and, with the spring in an at-rest position spaced above the medium and having a character thereon of sufficient hardness to cause a distinct character to be printed; means responsive to an electrical signal for applying a force to said spring between said locus and said printer to cause the spring to flex downwardly to cause the character printer to deliver a blow to said medium and imprint thereon; and a body of elastomer beneath said medium and positioned to receive the downward blows of said character printer to cushion same and to supply a rebounding force to said character printer to cause the printer and spring to move rapidly back to the springs at-rest position.

2. The recorder of claim 1 wherein said body is mounted for sidewise movement only along the Y-axis of the recorder and wherein the spring extends in the X-axis direction and guide means carried by the body and engaging the spring to limit deflection thereof in the Y-axis direction due to rapid acceleration and deceleration of the b such. directi 3. In a high speed point plotting graphic recorder having a record medium upon which points are to be plotted, in combination therewith of a printing apparatus for printing said points on said medium at a speed of several hundreds of points per minute comprising a body mounted adjacent said medium; a character printer having a character thereon of sufficient hardness to cause a distinct character to be printed on the medium; means for actuating said character printer including means responsive to an electrical signal for generating a force and also including means connecting said force generating means to said character printer to position the latter in an at-rest position spaced above the medium and to cause the character printer to deliver a blow to said medium and imprint thereon responsive to actuation of said force generating means and further including resilient means biasing the character printer to its at-rest position; and a body of elastomer beneath said medium and positioned to receive the downward blows of said character printer to cushion same and to supply a suflicient rebounding force to said character printer to cause the printer to move back to the printers at-rest position prior to the time the character printer is to deliver its next blow to said medium.

References Cited UNITED STATES PATENTS RICHARD B. WILKINSON, Primary Examiner. JOSEPH W. HARTARY, Assistant Examiner. 

1. IN A HIGH SPEED POINT PLOTTING GRAPHIC RECORDER HAVING A RECORD MEDIUM UPON WHICH POINTS ARE TO BE PLOTTED, IN COMBINATION THEREWITH OF A PRINTING APPARATUS FOR PRINTING SAID POINTS ON SAID MEDIUM AT A SPEED OF SEVERAL HUNDREDS OF POINTS PER MINUTE COMPRISING A BODY MOUNTED ADJACENT SAID MEDIUM, A LEAF SPRING RIGIDLY ATTACHED TO SAID BODY AT ONE LOCUS ALONG ITS LENGTH AND HAVING A PORTION EXTENDING FROM SAID LOCUS TO OVERLIE SAID MEDIUM; A CHARACTER PRINTER MOUNTED ON THE EXTENDING PORTION OF SAID SPRING AND, WITH THE SPRING IN AN AT-REST POSITION SPACED ABOVE THE MEDIUM AND HAVING A CHARACTER THEREON OF SUFFICIENT HARDNESS TO CAUSE A DISTINCT CHARACTER TO BE PRINTED; MEANS RESPONSIVE TO AN ELECTRICAL SIGNAL FOR APPLYING A FORCE TO SAID SPRING BETWEEN SAID LOCUS AND SAID PRINTER TO CAUSE THE SPRING TO FLEX DOWNWARDLY TO CAUSE THE CHARACTER PRINTER TO DELIVER A BLOW TO SAID MEDIUM AND IMPRINT THEREON; AND A BODY OF ELASTOMER BENEATH SAID MEDIUM AND POSITIONED RECEIVE THE DOWNWARD BLOWS OF SAID CHARACTER PRINTER TO CUSHION SAME AND TO SUPPLY A REBOUNDING FORCE TO SAID CHARACTER PRINTER TO CAUSE THE PRINTER AND SPRING TO MOVE RAPIDLY BACK TO THE SPRING''S AT-REST POSITION. 